Vízügyi Közlemények, 1932 (14. évfolyam)
2. füzet - XII. Kisebb közlemények
computed depth, the downflow with a top cylinder is secured. On the other hand, if tf < t u, the apron is to be placed lower, the measure of this lowering being the difference of the two water levels d = t u —t f ; in this way the most favourable downflow and the least erosion will be obtained. 1 Another very successful means of protecting the river bed is the baffle weir at the end of the apron, such as the Rehbock's dentated baffle weir. (Fig. 27.) This simple construction, driving the jet off the bottom, protects the dam from dangerous erosion. Another advantage of this construction is, that the apron can be built shorter. But this baffle weir acts favourably only when it is built to a proper height corresponding to its distance from the toe of the dam, or from the orifice of the sluice ; this height can be determined reliably only by experiments. The effect of the baffle weir 011 the erosion at different tail water depth is shown in Figure 25, by dashed curves, from which it is evident that, the baffle weir is effective only in the case of downflow with a top cylinder. The protection of the river bed is served also by Pfletschinger's diverting table, which is usually constructed of wood or reinforced concrete, according to the soil conditions (Fig. 31). As in most cases it is located at the level of low water, it does divert the shooting jet from the bottom, but the hydraulic jump, i. e. the transition from shooting to streaming flow appears farther below the dam, therefore the banks have to be protected for a longer stretch. Whilst the construction itself is cheap enough, the bank protection works and their maintenance are expensive. For this reason it is advisable to locate the diverting table at such a depth that a hydraulic jump with a top cylinder shall be formed above it. IV. PARAGRAPH 51 OF ACT XXIII. 1885. By : BÉLA de KENESSE Y. The paragraph of the Hungarian Water Laws cited above runs as follows : „If openings of culverts and bridges on roads and railways are insufficient for the natural downflow of water, provided that this insufficiency is not due to works of later date, the owners of the roads and railways have, within a limited period, to carry out at their own expense the work securing sufficient downflow". The writer deals with the unsettled questions arisen in connection with this paragraph, and points out the defectiveness of the procedure of public administration, in consequence of which the commissioned engineer has not enough opportunity of getting acquainted with the details necessary for securing the proper protection of public and private interests. He gives examples of the consequences of this procedure. M. Kenessey points out that- the owners of all culverts and bridges on roads and railways are to be regarded as riparian proprietors, just like the owners of land situated along the banks of rivers. Consequently the proprietors of the former objects should be charged with all obligations prescribed in the 40th paragraph of the Water Act, which have hitherto affected only riparian proprietors and other parties who profit by keeping the water courses in good repair. The obligations 1 In the original text on page 96 t s z — t u
